What is the restoration frequency range for transmission systems?

The restoration frequency range for transmission systems is typically designed to provide a means of communication or signaling during the restoration process after a disturbance. In the context of electric power systems, this frequency range is crucial for the detection and response to grid issues.

The correct range of 59.75 to 61 Hz falls within the broader context of system frequency management. Normally, electric power systems operate at a nominal frequency of either 50 Hz or 60 Hz, depending on the region. In North America, including PJM, the standard frequency is set at 60 Hz. The specified range for restoration is slightly above the nominal level because it reduces the chances of false triggers during routine operations and ensures that signals sent for restoration are distinguishable from normal operating conditions.

In contrast, other ranges provided do not align with the operational norms for restoration signaling. For instance, the ranges mentioned in the other choices either fall below or well above the accepted thresholds and would not serve effectively as means of communication for restoration efforts. By keeping the restoration frequency close to the nominal value, but within a specific threshold, operators can efficiently and effectively manage the grid restoration process, minimizing risks and enhancing system reliability.